Nice shots! However, I'm pretty sure the one at the back is a wasp
Have you tried using magnifying filters? Like you, I do not have a macro-dedicated lense, they are quite costly and you don't use them too often. However, I have a set of Hoya HMC magnifying filters - +1, +2, +4, each digit signifying increasing diopters.
I'm not "qualified" enough to comment on the rest from here onwards, but diopter, P = 1/f (focal length), f caculated in metre if I remember my high school physics correctly. So you're able to bring down the focal length by attaching your magnifying filters (increase P, decreased focal length), and as a result of this you get the effect of a macro lense, technically. HOWEVER, I'm pretty sure there are some sort of complications, otherwise Canon wouldn't sell macro-dedicated lense, wouldn't they?

One thing I've heard of is internal reflection - be sure to get a coated filter if you can.
I don't know how they will work on a zoom lense - I have mine mounted on a 50mm f/1.8 lense (aperture control, who knows?). I'm pretty sure somebody else here can offer you better advice than me.
This is a pic using the filter, dramtically scaled down so as not to compete with your thread. My lense set is nearly identical with yours (I have a Rebel 300D). You might be able to replicate the same pic with the EF-S lense, but to get so much detail will probably means that you have to get in real close, and often you will end up filling your whole eyepiece with the subject and you can't get the sharp detail in your picture. And then there is barrel distortion.